Iran's new president isn't waiting around for the United States and Iran to break decades of diplomatic silence — which they are expected to do later Thursday — before taking on the most divisive issue between the two countries: Iran's nuclear program.

Iranian President Hassan Rouhani told the United Nations General Assembly Thursday that "any use of nuclear weapons is a violation of the UN charter and a crime against humanity."

"As long as nuclear weapons exist, the threat of their use exists," he said Thursday morning.

"Israel, the only non-party to the Non-Proliferation Treaty in this region, should join thereto without any further delay," Rouhani said, ahead of a meeting between Iranian Foreign Minister Javad Mohammad Zarid, US Secretary of State John Kerry and their counterparts from China, Russia, France, Germany and Britain.

Kerry and Zarif's expected meeting would mark the first person-to-person diplomatic contact between the two nations since Iran's 1979 Islamic revolution.

The United States and other Western nations fear Iran is using its nuclear program to build a bomb — a charge Tehran denies. The standoff has strained relations between the United States and Iran for years.

"If it’s 3 months that would be Iran’s choice, if it’s 6 months that’s still good. It’s a question of months not years."

Speaking of which, Rouhani told the UN the pursuit of nuclear weapons is not appropriate for a nation under the mandate of Islam. According to The Washington Post, the Iranian leader told the assembly:

“Nuclear weapons and other weapons of mass destruction have no place in Iran’s security and defense doctrine, and contradict our fundamental religious and ethical convictions.”

Rouhani, who is in New York for the UN meeting, also hinted at further reconciliation if the nuclear problem could be resolved.

"After resolution of the nuclear issue there are no impossibilities in terms of advancing other things forward," he said, according to BBC News. "Everything is possible after the settlement."

Iran has been in on-and-off talks with the UN Security Council about its nuclear program since 2006.

Watch Rouhani's Thursday address in full here:

Iran's new leader has been giving numerous media interviews since his arrival in the United States, appearances that have differed demonstrably from those of former Iranian President Mahoud Ahmadinejad.

For example, when CNN's Christiane Amanpour asked Rouhani about the Holocaust — an event Ahmadinejad denied ever happened —he said, "any crime or — that happens in history against humanity, including the crime that the Nazis committed towards the Jews, as well as non-Jewish people, is reprehensible and condemnable, as far as we are concerned," said BBC.

Rouhani, who was elected in June, also took Iran's only Jewish parliamentarian with him to the UN event in New York.

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